Water supply

Water supply in Western Australia is currently made up with water from groundwater, desalination, and our dams.

The use of these three water sources currently differs from town to town across WA, depending on the location and climate conditions of that area.

Perth's water supply

Perth's water supply consists of water from all 3 main sources. With the largest population in WA, and a steady decline in average rainfall, the use of all 3 water sources is important in order to make sure there is enough water for everybody.

Regional Western Australia

Regional water supply consists mostly of groundwater and dam water with a small amount of desalination used in some areas. Depending on location, size and climate, different towns and cities will source their water from different places.

Our sources

Dams are storage reservoirs constructed to help collect and hold rainwater. They are built in rivers and have traditionally provided the majority of water for many towns and cities in Western Australia, particularly in Perth. While dams in the north west of Western Australia continue to receive enough rainfall to supply connecting towns, a shortage of rainfall in the south west has meant that dams in the area are increasingly being used to store and move water around.

Capture and storage

The way water is captured and stored in changes depending on the time of dam. Currently in Western Australia we use 4 different types of dams:

Main dams: a major reservoir in a valley which supplies water directly to users

Pipeheads: a small dam that has been diverted from a river that stores water and supplies directly to users

Pumpbacks: similar to a pipehead, pumpbacks divert water from a river and then pump water to storage reservoirs

Diversion dams: a dam that diverts a river straight into an irrigation system for use on crops and farmland

Treatment

Water from dams that is used for drinking water purposes has to undergo a process called mineralisation. During mineralisation, chlorine is added to the water to disinfect and clean the water, as well as fluoride to help prevent tooth decay.

Once the water has been treated it is then pumped through a network of pipes, pumps and reservoirs into the water supply.

Groundwater is water located in the space between soil and rock beneath the Earth’s surface and is an important part of water supply in Perth and Western Australia.

Storage

Groundwater is stored in aquifers which consist of underground layers of rock or sand that can absorb and hold water.

The water stored in these aquifers can be made up of rainwater that has filtered through the Earth's surface into the aquifer, or of recycled water which has been pumped back into the aquifer through the process of groundwater replenishment.

The ability of the water to move freely underground depends on the type of rock and whether the aquifer is unconfined or confined. In Perth there are three layers of aquifers:

Superficial aquifer: The shallowest aquifer which stretches across the coastal plain. Superficial aquifers are located closer to the surface and often express themselves as wetlands or lakes.

Confined Leederville aquifer: Below the superficial aquifer, and is separated by confining layers which minimises water movement. The Leederville aquifer is often several hundred metres thick, and in some areas it connects with the surface.

Confined Yarragadee aquifer: The oldest aquifer that contains a large supply of water because of its vast storage and limited connection to the surface environment.

Extraction

Groundwater is extracted from the aquifers with the use of bores. Bores can be used on a small scale by households, local councils and businesses to water gardens, lawns, parks and ovals or on a larger scale to extract water for a town or city's water supply.

Treatment

Before the groundwater is safe to drink, it has to undergo 4 different stages of treatment:

Aeration: the process of removing any trapped gasses and adding oxygen by spraying the water into the air.

Clarification: the removal of any sediment in the water

Filtration: the filtering stage which removes any leftover particles that remain once clarification has occurred

Mineralisation: the process of adding chlorine to disinfect the water and fluoride to protect against teeth decay.

Once the water has been treated it is then pumped through a network of pipes, pumps and reservoirs into the water supply.

Desalination is the process of removing salt from sea water to produce water that is more for drinking or for use by industries that require very pure water. Desalination provides a reliable water supply to cities and towns with minimal rainfall that are located close to the ocean, such as Perth.

There are currently two desalination plants located in Western Australia in Kwinana and Binningup.

Sourcing the water

The first stage in the desalination process is drawing water out of the ocean through the use of a seawater intake.

Treatment

Screening: during this process, any large objects that have entered the plant from the seawater intake are removed.

Filtration: this process helps to remove any remaining solid materials left over from the screening process

Dual media filter: this process helps to remove any last remaining solid materials from the screening and filtration process

Reverse osmosis: once all solid objects have been removed from the water, the reverse osmosis process removes the salt from the water by pushing the water through a membrane with large amounts of force

Energy recovery: the energy recovery units help to recapture and feed back into the system as most of the energy that is used during the treatment process comes from reverse osmosis.

Diffuser:salt that was removed from the water during the reverse osmosis process is then dispersed back out into the ocean

Mineralisation: the fresh water is then diverted to a mineralisaton tank where chlorine is added to disinfect and clean the water, as well as flouride to help prevent tooth decay

Storage tank: the water that has been through the mineralisation process is then pumped to a storage tank which is then later added to the water supply.

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